This invention relates to an apparatus for enabling deaf persons to converse over ordinary pushbutton telephone instruments and more particularly to a communicator and system employing an encoding technique and control key selection designed to minimize user fatigue and to enhance rate of word transmission during a normal conversation between deaf users.
Various systems have been disclosed for communicating data by using the pushbutton telephone set as a communications instrument. Flanagan et al in U.S. Pat. No. 3,675,513 describes a pushbutton telephone-teletypewriter communications system wherein encoded teletypewriter functions can be sent from either a special typewriter or a standard pushbutton telephone over telephone lines to a receiving typewriter for producing a permanent record of information received. Flanagan utilizes an encoding scheme requiring as many as four pushbutton strokes for selection of alphabetic characters. Multiple actuation is required of selected control keys for character selection. Steury in U.S Pat. No. 3,870,821 describes an improvement in pushbutton telephone communications systems of the general type described by Flanagan wherein a code chart display for indicating the particular set of characters, symbols or function signals is required. Selection and transmission of a desired alpha character can require three pushbutton actuations if an alpha portion of an alphanumeric message is transmitted by a device constructed as taught by Steury.
It is an object of this invention to provide an apparatus to deaf users for communicating over standard pushbutton telephones wherein a visual indication of a received or transmitted alphabetic character is provided and transmission of an alphabetic character requires a maximum of only two pushbutton strokes.
It is an object of this invention to provide an apparatus to deaf users so that anyone can communicate to a deaf user over the telephone system using standard pushbutton telephone tones.
Another object of the invention is to lessen user fatigue by providing an encoding scheme in which a user can comfortably use both hands and needs only to stroke a single pushbutton with each hand for selection of any alphabetic character.
Another object of the invention is to provide an easily identified and remembered alphabetic encoding scheme which takes advantage of the customary arrangement of markings on the standard pushbutton telephone keyboard coupled with assignment of control functions which are related to a pushbutton's relative position with respect to other pushbuttons.
Another object is to eliminate the need for an alphabetic code conversion chart.
A further object is to provide a deaf user with the capability of sending numbers and special symbols in selectable special modes where the coding scheme insures against accidental selection of a numeric symbol or other special mode by a user.
Another object is to minimize the number of pushbutton strokes required to send a series of numbers or special symbols once a user is in a numeric or other special mode.
A further object is to provide an inexpensive portable, self-powered and pocketsize communicator to deaf persons.
These and other objects of the invention are accomplished in accordance with the principles of this invention by implementing a coding scheme wherein pushbuttons of a standard pushbutton telephone set are assigned control functions related to their positional order. Preferably, actuation of the left-most lower pushbutton followed by actuation of a pushbutton having alphabetic symbols thereon effects transmission of the left-most indicated alphabetic letter. Actuation of the center lower key followed by actuation of a pushbutton having alphabetic symbols thereon causes transmission of the center indicated alphabetic letter. Similarly, actuation of the lower right pushbutton causes the right-most letter of a subsequently actuated pushbutton to be transmitted.
A user achieves rapid conversation transmission rates by using three fingers of a selected hand to actuate pushbuttons having control functions and the fingers of his other hand to actuate the remaining pushbuttons of the pushbutton telephone. Only one finger of each hand is thereby required for transmission of a selected alphabetic character. Physical effort required for tactile actuation of the pushbuttons is evenly divided between both hands and fatigue is minimized. Tactile effort related to control functions is distributed among a plurality of fingers of a selected hand to additionally lessen user fatigue.
The coding scheme is easily learned and remembered as a result of the positional ordering of control pushbuttons and their positional relation to the visual grouping of alphabetic characters appearing on the remaining pushbuttons.
Additional special transmission modes are provided for transmitting, for example, numbers and special symbols particularly adapted for the deaf, or the like. To ensure against inadvertent transfer from the normal alphabetic mode to a special mode, the code preferably calls for multiple actuation of a selected pushbutton to switch the communicator into a special mode. Once in the special mode, however, the user at his option sends a series of characters or symbols within the same mode by single pushbutton strokes corresponding to a selected character or symbol. User fatigue is thereby minimized and rate of transmission thereby enhanced for the commonly occurring situation in normal conversation wherein, for example, a series of numbers is to be sent. A user actuates a selected pushbutton with a single stroke to return to the normal alphabetic mode.